One of the most common items to replace on your car or truck is the oxygen sensor. Sometimes also known as the o2 sensor, this sensor is responsible for determining is the engine needs to add or remove some fuel from the air/fuel ratio. Due to this, a bad oxygen sensor should easily make your car not pass smog, and not passing emissions would require you to get a new oxygen sensor.

Most of the new cars, that are OBD2, have a total of two oxygen sensors… some might have more. Usually, there is an oxygen sensor that is in front of the catalytic converter, and another that is behind the catalytic converter. The one before is responsible for determining the air fuel mixture. The one after is only there to ensure the catalytic converter is working.

The oxygen sensor is basically a sensor with a harness plug on the end of it. There are cheaper alternatives that do not have a harness, and those are just universal that you would have to splice and add into your existing harness. This could get messy, and we don’t recommend it. Get a quality oxygen sensor such as Bosch or Denso, and make sure it has an OEM harness.

Now, replacing the oxygen sensor is very easy. All you need to do is to get an oxygen sensor socket, and slide it over the stock sensor. For most cars, the sensor will be in the exhaust headers somewhere before they bend down under the oil pan, or they could be on your factory downpipe, also around the bend. All you need to do is use the socket to unscrew the old sensor, and then screw the new one back in. Check your manual on the proper foot lbs of torque to tighten it to. You would do the same for the secondary o2 sensor that is after the catalytic converter.

Buy a replacement oxygen sensor.

Here is a video from CarMD on how to change an oxygen sensor:

Follow the video above on how to replace the oxygen sensor.